Torque converters in vehicles allow transmission of rotational output from a propulsion (e.g., an internal combustion engine and/or an electric motor) to a transmission. A torque converter transmits propulsion output to transmission input, increasing or maintaining the rotation speed of the transmission to the rotation speed of the propulsion. However, some of the propulsion output can be lost as a torque loss in the torque converter. To reduce the torque loss, a torque converter clutch can lock the torque converter to the propulsion, directly transmitting rotation from the propulsion to the transmission. However, it is a problem to identify when torque converter clutches can be operated to reduce torque loss, and to adjust operation of a vehicle to lock a torque converter clutch to reduce the torque loss.